Method of fastening a printing plate on a cylinder in a printing press and device for said fastening

ABSTRACT

Method and apparatus for fastening a printing plate to the plate cylinder of a printing press. One edge of the printing plate is positioned against a pair of projections provided as part of a clamping assembly for clamping the aforementioned edge. The printing plate is substantially wrapped about a plate cylinder and the opposite edge is coupled to a second clamping assembly which in turn is provided with a pivot pin having an arm pivotally mounted thereto. The arm is provided with a roller which rollingly engages the sidewall of a recess provided in the printing cylinder. A first wedge shaped member is threadingly engaged by a threaded fastener which is secured to the second clamping assembly. A second wedge shaped member slidably engages the first wedge shaped member and moves away from the first wedge shaped member as the aforesaid threaded fastener is tightened thereby causing the pivotal arm to rotate about the axis of the roller member to draw the printing plate more tightly about the printing cylinder. Thus the printing plate is secured by three triangularly positioned points two of which are stationary and the third of which is movable to automatically compensate for any sidewise movement of the printing plate.

United States Patent 1191 Dyrberg et al.

1 Apr. 22, 1975 METHOD OF. FASTENING A PRINTING PLATE ON A CYLINDER IN APRINTING PRESS AND DEVICE FOR SAID FASTENING [75] Inventors: IngvaldDyrberg, Sollentuna; Algot Ingemar Eriksson, Solna. both of Sweden [73]Assignee: AB Printing Equipment, Sollentuna.

Sweden 22 Filed: Feb. 1, 1974 1211 Appl. No.: 438,552

Related US. Application Data 163] Continuation of Ser. No. 269.703. July7, 1972.

abandoned.

[30] Foreign Application Priority Data July 12. 1971 Sweden 9012/71 [52]U.S. Cl 10l/4l5.1; 101/426 [51] Int. Cl B4lf 27/12 [58] Field of Searchl0l/4l5.1. 378, 426

[56] References Cited UNITED STATES PATENTS 1,966.121 7/1934 Hotchkiss101/415.1 2.123.997 7/1938 Jironsck 101/415.1 2.737.887 3/1956 Gcrickel01/9l5.1 2.768.579 10/1956 Fies 101/415.l

3.119.331 1/1964 Koch et a1. 10l/415.1

3.311.052 3/1967 Zcnthen 101/4151 3.583.318 6/1971 Stevenson 101/415.I

Primary Examiner-Edgar S. Burr Assistant E.\'aminerWilliam PiepazAttorney. Agent. or Firm-Ostrolenk, Faber. Gerb & Soffen [57] ABSTRACTMethod and apparatus for fastening a printing plate to the platecylinder of a printing press. One edge of the printing plate ispositioned against a pair of projections provided as part of a clampingassembly for clamping the aforementioned edge. The printing plate issubstantially wrapped about a plate cylinder and the opposite edge iscoupled to a second clamping assembly which in turn is provided with apivot pin having an arm pivotally mounted thereto. The arm is providedwith a roller which rollingly engages the sidewall of a recess providedin the printing cylinder. A first wedge shaped member is threadinglyengaged by a threaded fastener which is secured to the second clampingassembly. A second wedge shaped member slidably engages the first wedgeshaped member and moves away from the first wedge shaped member as theaforesaid threaded fastener is tightened thereby causing the pivotal armto rotate about the axis of the roller member to draw the printing platemore tightly about the printing cylinder. Thus the printing plate issecured by three triangularly positioned points two of which arestationary and the third of which is movable to automatically compensatefor any sidewise movement of the printing plate.

3 Claims, 4 Drawing Figures METHOD OF FASTENING A PRINTING PLATE ON ACYLINDER IN A PRINTING PRESS AND DEVICE FOR SAID FASTENING This is acontinuation of application Ser. No. 269,703, filed July 7, I972, nowabandoned.

Offset printing is done from a plate which is fastened on a printingroller, and from which the impression is transferred via a rubber rollerto the paper.

For a correct fit the tightening of the plate is very important. Theregister is adjusted to the front edge of the plate with adjustingscrews and various means, but there must be a perfect register over thewhole surface of the plate. Especially in colour printing even thesmallest error in alignment is clearly visible from a consideration ofthe product printed from the plate.

The tightening of the plate must be done with an even tension over thewhole plate surface, so that blistering or buckling does not occur, butat the same time the tension must not be so great that the plate isstretched at any point, especially in zinc plates; or splits, as easilyoccurs with aluminium plates. The forces which occur in printing arerelatively great and the plate is subjected to a constant mangling whichtends to pull the picture backwards.

For mounting the plate in the press there are two elongated memberstypically referred to as rulers which are located in an axial channel inthe surface of the plate cylinder. The plate is fastened on these rulerswith a number of screws in a known manner. In order to get the requiredeven plate tension one has then previously had a number of turnbuckleswith possibilities of adjustment in each ruler, whereby it becamepossible to stretch the plate locally more or less at various places.Another method of obtaining even tension in the plate has been to mounta large number of springs between the rear ruler and the plate cylinder.which springs even out the differences in tension in the various partsof the plate for obtaining an even tension. By fastening the plate ontop of springs the plate has also a certain lateral mobility at its rearedge.

The present invention relates to a completely new method of achievingthe even tension and stretching of the plate without time-consumingadjustment with a large number of turnbuckles which were previouslyrequired or a tightening which is not completely satisfactory, which isobtained with springs between the rear ruler and the cylinder.

The invention is characterized in that the plate is tightened at threetriangularly positioned points, and that the device for tightening ofthe rear edge consists of a bearing which can roll freely against therear edge of the cylinder channel.

The construction will be more closely described in the form of anexample according to the enclosed drawing in which FIG. 1 shows a topview of a printing plate cylinder embodying the principles of thepresent invention.

FIG. 2 shows a detailed view of a portion of the printing plate mountingassembly of FIG. 1 wherein one of the ruler members has beensectionalized to facilitate observation of the components positionedtherebeneath;

FIG. 3 shows a sectional view of the structure of FIG. 2 looking in thedirection of arrows 3--3; and

FIG. 4 shows an end view of the structure of FIG. 2 looking in thedirection of arrows 4-4.

FIG. 1 shows a plate 1 fastened to ruler assemblies 2 and 3. The frontruler assembly is comprised of two elongated members 2a and 21; securedto one another by screws 4 to clamp the front edge 1a of plate 1therebetween, as shown best in FIG. 4. The member 2b is provided withprojections 8 and 9, as shown best in FIG. 1, which rest against oneedge 6a of the channel 6 provided in the printing plate cylinder 5. Theprojections 8 and 9 abut against edge 6. Cylinder 5 is provided withside edges 7 and 10 which engage the ends of ruler assembly 2 to preventlateral movement of assembly 2 and hence plate 1. Thus, the front edgeIn of printing plate 1 is effectively secured at two points 8 and 9.

After the front edge of the plate has been secured to ruler assembly 2in the manner set forth hereinabove. the plate is stretched aboutprinting plate cylinder 5 and its rear edge 1b is positioned betweenruler assembly 3 comprised of rigid members 3a and 3b secured to oneanother by screws 4. The printing plate is firmly and uniformlystretched about printing plate cylinder 5 by the adjustment of anadjustable screw 11 which extends through untappedopening 19 in rulermember 312. The head 11a of adjustable screw 11 is positioned within acavity 20 provided in member 3a. This cavity communicates with anopening 21 in member 3a so as to permit insertion of the head of a screwdriver. for example, for rotating and hence adjusting adjustable screw11. Screw 11 threadedly engages a tapped opening provided in awedge-shaped member 12 which has a wedge surface 13 in slidableengagement with a corresponding wedge surface 14 provided on a pivotallymounted arm 15. Arm 15 is swingably mounted about a pivot pointcomprised of bolt 16 which extends through an untapped opening 15a inarm 15 and which threadedly engages a tapped'opening 22 in member 312.Considering FIG. 2, arm 15. may be caused to rotate in the clockwisedirection as shown by arrow B which clockwise rotation occurs in amanner to be more fully described hcreinbelow.

Member 15 is further provided with a cavity 15a for receiving a bearing17 mounted to a shaft 17a which is fixedly secured within an opening1512 which communicates with cavity 15a, as shown best in FIG. 3.Bearing 17 is free-wheelingly mounted about shaft 17a and has a portionof its periphery engaging the side wall 18 of channel 6 provided in theprinting plate cylinder 5.

By tightening the screw 11, wedge-shaped member 12 is urged in thedirection shown by arrow C of FIG. 4, causing arm 15 to rotate in theclockwise direction B (FIG. 2) which urges bearing 17 downwardly, asshown by arrow D of FIGS. 2 and 4, against the side wall 18 of channel6. This, in turn, moves ruler assembly 3 in the upward direction, asshown by arrow E of FIGS. 2 and 4, so as to tightly wrap the printingplate 1 about cylinder 5.

The plate 1 is thereby fixed at three points, namely points 8, 9 and 17and since the friction of the needle bearing 17 is so small, the rulerassembly 3 is free to move in the lateral direction during thestretching of the plate so that any oblique tensions which may occur areeliminated.

The side wall 18 of channel 6 opposes the pulling pressure applied toside wall 18 by the tightening of plate 1. Since there is minimalfrictional resistance between bearing 17 and side wall 18, bearing 17may roll freely along side wall 18 if oblique tensions exist in theplate and thereby balance such tensions out. For example, consideringFIG. 2, ifthe tensions imposed by plate 1 upon the ruler assembly 3 aregreater'to the left of bearing 17 (relative to FIG. 2) the rulerassembly 3 will pivot clockwise about the bearing 17 and bearing 17will'thereby be free to move laterally to balance the unequal tensionsapplied upon arm 15. Conversely, if the tensions applied by the printingplate 1 upon ruler assembly 3 and to the right of bearing 17 are greaterthan the tension applied to ru'ler assembly 3 to the leftof bearing 17,then bearing 17 is again free to move laterally to balance these unequaltensions. The pressures developed between bearing 17 and side wall 18are relatively high and it has been shown that with the small bearingdimensions employed-herein, the best results are achieved by usingneedle bearings.

-' What is claimed is:

1,. A method for fastening a printing plate to a printing plate;cylinder in a printing press at three spaced points. said three pointsdefining a triangle comprising the steps of:

. swingably mounting the first end of an arm towsaid second rulerassembly;

providing a rollable bearing upon said swing arm at j a pointintermediate the ends of said swing arm; providing a wedging surface atthe free end of said swing arm; 7 positionjng the surface of a wedgemember against it the wedge surface provided. at the free end of saidswing arm;

positioning said second ruler assembly in said channel with said bearingresting against said second sidewall;

moving said wedge member toward said swingablc arm by means of a screwto rotate said swing arm about its pivot point thrcby urging the bearingof fsaid swing arm against the remaining side wall ofsaid channelcausing the second ruler assembly to move away from said second sidewall, and thereby tightening said printing plate about said printingplate cylinder, said rollable bearing being the third point of contactof said printing plate with said printing cylinder, whereby saidrollable bearing is free to move laterally in order to relieve uneventensions applied by said printing plate to the second ruler assembly.

2. Apparatus for uniformly tightening a thin printing plate on a platecylinder in a printing press. said cylinder having a channel extendingthe length of said cylinder, said channel having first and second spacedside wall portions;

a first elongated ruler assembly;

means for securing one marginal edge of said printing plate to saidfirst ruler assembly;

one edge of said first ruler assembly having first and second spacedprojections being positioned to bear against said first side wall;

a second ruler assembly for securing the remaining marginal edge of saidplate; v

an arm having a first end pivotally secured to said second rulerassembly;

the free end of said arm having a wedge-shaped cross-section to providea first wedge surface;

a wedge member being positioned to have one surface thereof in slidingengagement with said first wedge surface;

said wedge member having a tapped aperture; a

screw member threadedly engaging said tapped aperture; said second rulerassembly having an opening in alignment with the tapped aperture in saidwedge member;

a rollable bearing mounted on said arm intermediate its ends;

said bearing being positioned to rollingly engage said second side wall;

said wedge member being adapted to swing the free end of said swing armtoward said second side wall when said screw member is tightened to urgethe wedge member toward the second ruler assembly and move the bearingtoward the second side wall causing said second ruler assembly to moveaway from said second side wall;

said bearing being the only contact between said second side wall andsaid second ruler assembly whereby said plate is secured to saidcylinder at only three points. said first and second projectionsconstituting two of said three points and said bearing being the thirdpoint, whereby the rolling engagement between said bearing and saidsecond side wall permits lateral movement of said second ruler assemblyto assure the application of uniform tension upon said plate by saidfirst and second ruler assemblies.

3. The apparatus of claim 2 wherein said bearing is a needle bearingl

1. A method for fastening a printing plate to a printing plate cylinderin a printing press at three spaced points, said three points defining atriangle comprising the steps of: affixing a first marginal edge of theprinting plate to a ruler assembly; providing a channel in the printingplate cylinder having first and second spaced parallel side walls;providing two projections along said ruler assembly, said twoprojections abutting against said first side wall of said channel;wrapping said printing plate around the cylinder and securing theopposite marginal edge of said printing plate to a second rulerassembly; swingably mounting the first end of an arm to said secondruler assembly; providing a rollable bearing upon said swing arm at apoint intermediate the ends of said swing arm; providing a wedgingsurface at the free end of said swing arm; positioning the surface of awedge member against the wedge surface provided at the free end of saidswing arm; positioning said second ruler assembly in said channel withsaid bearing resting against said second side wall; moving said wedgemember toward said swingable arm by means of a screw to rotate saidswing arm about its pivot point threby urging the bearing of said swingarm against the remaining side wall of said channel causing the secondruler assembly to move away from said second side wall, and therebytightening said printing plate about said printing plate cylinder, saidrollable bearing being the third point of contact of said printing platewith said printing cylinder, whereby said rollable bearing is free tomove laterally in order to relieve uneven tensions applied by saidprinting plate to the second ruler assembly.
 2. Apparatus for uniformlytightening a thin printing plate on a plate cylinder in a printingpress, said cylinder having a channel extending the length of saidcylinder, said channel having first and second spaced side wallportions; a first elongated ruler assembly; means for securing onemarginal edge of said printing plate to said first ruler assembly; oneedge of said first ruler assembly having first and second spacedprojections being positioned to bear against said first side waLl; asecond ruler assembly for securing the remaining marginal edge of saidplate; an arm having a first end pivotally secured to said second rulerassembly; the free end of said arm having a wedge-shaped cross-sectionto provide a first wedge surface; a wedge member being positioned tohave one surface thereof in sliding engagement with said first wedgesurface; said wedge member having a tapped aperture; a screw memberthreadedly engaging said tapped aperture; said second ruler assemblyhaving an opening in alignment with the tapped aperture in said wedgemember; a rollable bearing mounted on said arm intermediate its ends;said bearing being positioned to rollingly engage said second side wall;said wedge member being adapted to swing the free end of said swing armtoward said second side wall when said screw member is tightened to urgethe wedge member toward the second ruler assembly and move the bearingtoward the second side wall causing said second ruler assembly to moveaway from said second side wall; said bearing being the only contactbetween said second side wall and said second ruler assembly wherebysaid plate is secured to said cylinder at only three points, said firstand second projections constituting two of said three points and saidbearing being the third point, whereby the rolling engagement betweensaid bearing and said second side wall permits lateral movement of saidsecond ruler assembly to assure the application of uniform tension uponsaid plate by said first and second ruler assemblies.
 2. Apparatus foruniformly tightening a thin printing plate on a plate cylinder in aprinting press, said cylinder having a channel extending the length ofsaid cylinder, said channel having first and second spaced side wallportions; a first elongated ruler assembly; means for securing onemarginal edge of said printing plate to said first ruler assembly; oneedge of said first ruler assembly having first and second spacedprojections being positioned to bear against said first side waLl; asecond ruler assembly for securing the remaining marginal edge of saidplate; an arm having a first end pivotally secured to said second rulerassembly; the free end of said arm having a wedge-shaped cross-sectionto provide a first wedge surface; a wedge member being positioned tohave one surface thereof in sliding engagement with said first wedgesurface; said wedge member having a tapped aperture; a screw memberthreadedly engaging said tapped aperture; said second ruler assemblyhaving an opening in alignment with the tapped aperture in said wedgemember; a rollable bearing mounted on said arm intermediate its ends;said bearing being positioned to rollingly engage said second side wall;said wedge member being adapted to swing the free end of said swing armtoward said second side wall when said screw member is tightened to urgethe wedge member toward the second ruler assembly and move the bearingtoward the second side wall causing said second ruler assembly to moveaway from said second side wall; said bearing being the only contactbetween said second side wall and said second ruler assembly wherebysaid plate is secured to said cylinder at only three points, said firstand second projections constituting two of said three points and saidbearing being the third point, whereby the rolling engagement betweensaid bearing and said second side wall permits lateral movement of saidsecond ruler assembly to assure the application of uniform tension uponsaid plate by said first and second ruler assemblies.